Integrated circuits are typically housed within a package adapted for mounting to a printed circuit board. Exemplary packages include "flip-chip" packages and multi-chip module circuit packages fabricated with electric tapes. Flip-chip packages prove particularly valuable because they efficiently utilize space when employed with very large scale integrated (VLSI) circuits.
Flip-chip packages include a die and a plurality of contact pads located on a surface of the die. The die forms an integrated circuit. The integrated circuit is electrically coupled with the contact pads located on the surface of the die via electrically conductive paths. The contact pads can form an array of contact pads that cover the surface of the die. In addition, the contact pads on the surface of the die can be generally divided into two types: energizing contact pads for powering and grounding the integrated circuit; and data contact pads for transmitting to and receiving data from the integrated circuit.
FIG. 6 shows the bottom surface of a die and the typical arrangement of contact pads on the die. The array of contact pads on the surface of the die are illustrated as an array of boxes. The energizing contact pads, indicated by a box with an "X" inside, are positioned along the outer-most row of the array of contact pads. Accordingly, the data contact pads are located within a frame of power and ground contact pads.
Flip-chip packages can also include a substrate. FIG. 7 illustrates the top surface of a substrate for mounting to the bottom surface of the die shown in FIG. 6. The substrate has a plurality of mating contact pads positioned on the top surface of the substrate. The die can be mounted and electrically coupled to a substrate by aligning and connecting the contact pads on the die with the mating contact pads on the substrate. Typically, solder balls are soldered between the contact pads on the die and the mating contact pads on the substrate to connect the die and the substrate.
The mating contact pads on the substrate include energizing contact pads and data contact pads. The mating contact pads on the surface of the FIG. 7 substrate are illustrated as an array of boxes. The energizing contact pads on the substrate are indicated with a box having an "X" inside. The substrate's energizing contact pads are positioned so that they align with the energizing contact pads on the bottom surface of the die shown in FIG. 6.
The substrate can also include external connectors, such as connecting pins or solder balls, located on another surface of the substrate. One end of each of the external connectors is internally connected, through electrical routing paths within the substrate, to the mating contact pads on the substrate. The other end of each of the external connectors is electrically coupled to conductive paths in a printed circuit board. This configuration electrically couples the integrated circuit of the flip-chip package with the printed circuit board.
The substrate is typically a multi-layered structure that provides paths for fanning out all the electrical connections from the die to the external connectors of the substrate. The substrate also includes vias that route signals between the layers of the substrate. The FIG. 7 vias are illustrated as circles that are connected to the energizing contact pads by electrically conductive paths on the substrate surface. One via is connected to each energizing contact pad. The energizing pad and via combination utilizes space along the edge of the substrate, thereby inhibiting the ability of data lines to reach the edge of the substrate.
For many integrated circuits, the size of the die in a flip-chip package is determined by the density of connections to the integrated circuit housed within the die. In the current design of flip-chip packages, the contact pads are not structured or positioned in an order that maximizes the density of connections to the die.
Accordingly, there is a need for a flip-chip package having contact pads structured in a manner that increases the density of data line connections along the edge of the substrate.